Tuxedo (Transactions for Unix, Extended for Distributed Operations) is a middleware platform used to manage distributed transaction processing in distributed computing environments. Tuxedo is a transaction processing system or transaction-oriented middleware, or enterprise application server for a variety of systems and programming languages. Developed by AT&T in the 1980s, it became a software product of Oracle Corporation in 2008 when they acquired BEA Systems. Tuxedo is now part of the Oracle Fusion Middleware.

From the beginning in 1983, AT&T designed Tuxedo for high availability and to provide extremely scalable applications to support applications requiring thousands of transactions per second on commonly available distributed systems. The original development targeted the creation and administration of operations support systems for the US telephone company that required online transaction processing (OLTP) capabilities.

The Tuxedo concepts derived from the Loop Maintenance Operations System (LMOS). Tuxedo supported moving the LMOS application off mainframe systems that used Information Management System (IMS) from IBM on to much cheaper distributed systems running (AT&T's own) Unix.

The original Tuxedo team comprised members of the LMOS team, including Juan M. Andrade, Mark T. Carges, Terrence Dwyer, and Stephen Felts. In 1993 Novell acquired the Unix System Laboratories (USL) division of AT&T which was responsible for the development of Tuxedo at the time. In September 1993 it was called the "best known" distributed transaction processing monitor, running on 25 different platforms. In February 1996, BEA Systems made an exclusive agreement with Novell to develop and distribute Tuxedo on non-NetWare platforms, with most Novell employees working with Tuxedo joining BEA. In 2008, Oracle Corporation acquired BEA Systems, and TUXEDO was marketed as part of the Oracle Fusion Middleware product line.

Tuxedo has been used as transactional middleware by a number of multi-tier application development tools. The Open Group used some of the Tuxedo interfaces as the basis of their standards such as X/Open XA and XATMI.

The Tuxedo developers published papers about it in the early 1990s. Later it became the basis of some research projects.

Tuxedo is at its core a message routing and queuing system. Requests are sent to named services and Tuxedo uses memory-based inter-process communication facilities to queue the requests to servers. The requester is unaware of where the server that actually processes the request is located or how it is implemented. In essence, Tuxedo provided the elements of service-oriented architecture (SOA) decades before the phrase was coined. Tuxedo can use the content of the message to determine what servers should be utilized to receive the request by means of data-dependent routing.

The heart of the Tuxedo system is the Bulletin Board (BB). This is a shared memory segment that contains the configuration and state of a Tuxedo domain. Servers, services, transactions, and clients are all registered in the BB providing a global view of their state across the machines within a domain. To coordinate updates to the BB a process called the Bulletin Board Liaison (BBL) runs on each machine to keep the local copy of the BB up-to-date. A master machine runs a process called the "Distinguished Bulletin Board Liaison" that coordinates the updates to the BB. This allows each machine to have a view of what servers, services, transactions, and clients are on each machine within the domain.